Cache Fusion: Extending Shared-Disk Clusters with Shared Caches

Cache Fusion TM is a fundamental component of Oracle’s Real Application Cluster configuration, a shared-cache clustered-database architecture that transparently extends database applications from single systems to multi-node shared-disk clusters. In classic shared-disk implementations, the disk is the medium for data sharing and data blocks are shipped between nodes through disk writes and reads under the arbitration of a distributed lock manager. Cache Fusion extends this capability of a shared-disk architecture by allowing nodes to share the contents of their volatile buffer caches through the cluster interconnect. Using Cache Fusion, data blocks are shipped directly from one node to another using interconnect messaging, eliminating the need for extra disk I/Os to facilitate data sharing. Cache Fusion thus greatly improves the performance and scalability characteristics of shared-disk clusters while continuing to preserve the availability benefits of shared-disk architectures.